This Recommended Practice (RP) has been prepared to facilitate the execution of conceptual and detailed CP design using aluminium or zinc based galvanic anodes, and specification of manufacture and installation of such anodes. Whilst the requirements and recommendations are general, this document contains advice on how amendments can be made to include project specific requirements. The RP can also easily be amended to include requirements or guidelines by a regulating authority, or to reflect Owner's general philosophy on corrosion control by CP.

Some of the design recommendations and methods in Sections 5, 6 and 7 are also valid for CP systems using other current sources such as magnesium anodes and rectifiers (i.e. impressed current).

This RP is primarily intended for CP of permanently installed offshore structures associated with the production of oil and gas. Mobile installations for oil and gas production like semi-submersibles, jack-ups and mono-hull vessels are not included in the scope of this document. However, to the discretion of the user, relevant parts of this RP may be used for galvanic anode CP of such structures as well.

Detailed design of anode fastening devices for structural integrity is not included in the scope of this RP. Considerations related to safety and environmental hazards associated with galvanic anode manufacture and installation are also beyond its scope.

Compared to the 1993 edition of DNV-RP-B401, design considerations for impressed current CP have been deleted from the scope of the 2004 revision whilst the sections on anode manufacture and installation are made more comprehensive. CP of submarine pipelines is further excluded from the scope (see 1.5). However, this RP is applicable for CP of components of a pipeline system installed on template manifolds, riser bases and other subsea structures when such components are electrically connected to major surfaces of structural C-steel.

In this revision, guidance and explanatory notes are contained in a ‘Guidance note' to the applicable paragraph in Sections 6, 7, 8 and in Annex B and C. (Most of the Guidance notes are based on queries on the 1993 revision of DNV-RP-B401 and other experience from its use. Furthermore, some informative text in the old revision has been contained in such notes).

All tables and figures associated with Sec.6 are contained in Annex A. The document has further been revised to facilitate specification of Purchaser information to Contractor, and optional requirements associated with CP design, manufacture and installation of anodes (see 1.3). Additional comments on revisions in this 2004 issue are made in the Introduction (last paragraph) of Sections 6, 7, 8 and Annex B and C.